Walking from the elevators to my cubicle (I was only a summer intern, and hence had a cube, not an office) in the morning, I was greeted by an interesting interference pattern: there would be a counter grid of "dark spots", which unlike physical spots appeared large when one was far and got smaller as one approached...
https://www.inverse.com/article/41595-hermann-grid-illusion-...
(Scroll down)
He could tell what record he was looking at by sight by inspecting the groove patterns: number of tracks, track length, and even the patterns of the active part of the song itself. As I recall, he was proud that he once identified the 1812 overture from more than 10 feet away because of the placement of the grooves at the loud parts.
BTW, records didn't necessarily have constant spacing -- the cutter knew the amplitude of the part of the spiral plus/minus one rotation away so it could place the track close as possible without causing collisions. I believe that made it easier to identify songs.
"Dr. Arthur Lintgen, a Philadelphia physician, can — within prescribed limits — determine which works of classical music are present on a phonograph record by “reading” the record’s grooves. His ability is not the result of any trickery — he performs the feat by combining a thorough knowledge of classical music with the technique of determining the structure and dynamics of a piece of music by examining the spacing and pattern of the grooves."
Incidentally, a lot of sound engineers at the time would put tracks with less frequency dynamicism into those innermost rings to prevent records from skipping.
Think that over. On a 33 1/3 LP, the outermost groove takes 1.8 seconds to complete a rotation. The innermost groove takes... 1.8 seconds to complete a rotation. Hence, over the entire record, every single groove lines encodes 1.8 seconds of information and lines up exactly with its neighbor in terms of time elapsed. The inner grooves have less space to cover but they compensate by moving more slowly. It's weird but makes sense in a way that's reminiscent of Aristotle's wheel paradox ( https://en.wikipedia.org/wiki/Aristotle%27s_wheel_paradox )
On a perfectly mastered LP, any song whose bpm is a multiple of 33 1/3 would have these lined up rhythmic patterns. E.g. a song that clocks in at 100 bpm would have exactly 3 beats in every rotation. You could make a faster dance song line up by speeding up the motor to a fractional degree.
>Incidentally, a lot of sound engineers at the time would put tracks with less frequency dynamicism into those innermost rings to prevent records from skipping.
True, since the innermost grooves have less space to encode information, they have to wobble more in a given distance in order to maintain the same dynamic range. IIRC sometimes they would space those inner grooves further apart to give them more wobble room.
She's a beast.
Used to follow Oona on Google+, but forgot the name and haven't had a (working) RSS setup for the last few years so I hadn't read anything from her since then.
She's totally amazing when it comes to decoding signals, noticing effects and naming them (for example: there's a video on her YouTube channel with her filming a brick wall as she goes towards and back from a brick wall and she points out how the sound of a nearby waterfall changes.)
